عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Objective: To compare the effect of strains and levels of yeast on fattening calves. Design: 2"3 factoial affangement Animalls: Thirty five male Holstain calves(average live weight 296.8 kg) . Procedure: Animal were divded into five experimental goups each reciving a diet supplementd with one of the two strains yeast saccharomyces cerevisiae including Sc.47 (Biosaf) and (han mayeh) at tow different leves (expressed as x and 2x) or control diet (no yeast).The arnount ofx were 2.5 and 5 g /100 kg LWd for Biosaf and Iran mayeh, respectively. The diet containd forages and concentrate (70:30 ratio). Average daily gain and feed intake of each calf were measured during 1 35 days of the experimental period. At the end of the fattening period rumen liqure were obtained at 0,3 and 6 hours post -feeding. Blood samples were also taken at 0 and 3 hours post -feeding and subjected for the blood metabolites analaysis. Statistical analysis: The completely randomized desigin and the randomly complete blockdesign with analysis of covariance. Result: Growth rate was improved( p>0.05) in the animals using Biosaf at the level of x compared with those of contoral group (1457 vs1351lg/day). Despite that feed intake did not differed between the animals. the addition of Biosaf made cause a better feed conversion rate and higher rumen pH than the of other treatment. The total number of rumen bacteria was also increased numerically. No changes on blood serum metabolites were observed. Conclusion: The use of yeast Biosaf may result in a better stability of rumen pH and so increase rumen bacterial population which in turn can improve ruminal fermentation and growth rate in calves.